Sensor devices or sondes are used for measuring the quality of water. A sonde can contain several different water quality probes or sensors including sensors for turbidity, pH, dissolved oxygen, conductivity, temperature, salinity and possibly other water quality measurements. These measurements are typically made using optical and/or electrical means. If the optical pathway or the electrical contacts become contaminated with debris or fungal or algal growth, inaccurate measurements may be obtained.
It is known in the art to equip these sondes with sensors that include an optical window through which measurements are made as a function of reflectance, fluorescence or another optical or photosensitive response. However, in measurements involving extended, long-term deployments, extensive fouling by plant and animal species may accumulate onto the sensor, thereby preventing the sensors from making accurate measurements. Thus, this fouling limits present sensors to be used for short periods only before maintenance or manual clean-up is required. Furthermore, in aggressive fouling environments, the accumulation of debris or fungal or algal growth onto the sensors may result in a short period of time. Present sensors are not properly equipped to obtain accurate measurements in severe fouling environments for an extended period of time.
It is therefore desirable to provide a sensor device which may be used effectively and obtain accurate measurements in both extended, long-term deployments and also aggressive fouling environments.
This invention is directed to a sensor cleaning apparatus useful in obtaining accurate measurements for measuring multiple parameters of the quality of water in extended, long-term deployments and in aggressive fouling environments.
The sensor cleaning apparatus comprises a sonde having a sensor, a wiper element and a brush, wherein the brush extends from the wiper element. The brush is used to sweep across other sensors in the sonde and thereby prevent the build-up of debris and growth that may interfere with accurate measurements. Typically, the sonde will be programmed to rotate the brush/wipe arm with sufficient frequency to keep the sensors clean enough to provide effective measurements.
In one embodiment, the wiper element and the brush rotate about a common axis. In accordance with a more particular embodiment of the invention, the wiper element and the brush are carried on a common arm that extends radially from a motor-driven shaft about which the arm rotates. In still a more preferred manifestation of the invention, the wiper media on the wiper element is formed from a foamed rubber pad and the brush is imitation squirrel hair.
Another manifestation of the invention is a sonde including a turbidity sensor and a pH sensor wherein the turbidity sensor includes a rotatable shaft that carries a wiper and a brush. The brush extends beyond the outer diameter of the turbidity sensor and rotates to wipe away and remove debris and growth from the pH sensor. In another manifestation of the invention, a sonde includes a turbidity sensor and an oxygen sensor constructed in the same manner as the foregoing.
Because of the self-wiping feature of the present invention, it is ideal for use in extended, long-term deployments. In addition, it is virtually maintenance-free. The wiped sensors dramatically increase deployment times without increased site visits or maintenance costs. As a result, time and money can be saved through the use of the present invention in extended deployment times and in severe fouling environments in conducting water quality tests.